Guiding member in the form of a metal ring for assembly with friction and with the articulating and/or sliding capability of a shaft

ABSTRACT

The bore of the ring has workings suitable to act as a grease reserve at a friction area. A self-lubricating coating layer with a low wettability is applied to the entire surface of the bore, including in the workings suitable to act as a grease reserve, such that after wearing of the layer of self-lubricating coating at the friction surface of the bore, the difference in wettability between the friction surface and the workings still having the coating layer, enables the grease to be drawn out of the workings in order to lubricate the friction area.

The invention concerns a self-lubricating guidance device for any kind of articulation.

The invention has particularly advantageous applications for ring or rotary joints, or for slides with workings suitable to act as a grease reserve, with the aim of enabling lubrication only during assembly and/or lubrications at very long time intervals.

These workings suitable to act as a grease reserve can consist of holes, cells, grooves, grids, etc.

A solution of this type is covered in patent FR 2 882 409.

In this state of the art, the grease contained in the bottom of the workings suitable to act is a grease reserve has difficulties in positioning itself between, for example, the shaft and the bearing, in order to lubricate the contact and friction area.

This is notably the case when the workings suitable to act as a grease reserve are deep.

The result is that the grease tends to remain in the bottom of the workings and, after a time, is no longer able to fulfill its lubrication function in the contact area.

The invention is intended to remedy these disadvantages in a simple, safe, effective and rational manner.

The problem that the invention is designed to resolve is to enable continuous greasing in the workings within the ring or other component, so as to feed lubricant to the surfaces in contact during operation.

To resolve such a problem, a self-lubricating coating with low wettability is applied to the entire surface of the said bore, including in the workings suitable to act a grease reserve, such that after wearing of the layer of self-lubricating coating at the friction surface of the bore, the difference in wettability between the said friction surface and the workings still having the coating, enables the grease to be drawn out of the said workings in order to lubricate the said friction surface.

According to another characteristic, the low-wettability self-lubricating coating is based on PTFE, MoS2 or Graphite, for example.

The workings capable of acting as a grease reserve can be composed, in a known manner, of holes, cells, grooves (the which grooves can form a grid), chevrons, etc.

The invention will be explained below in more detail, with the aid of the appended drawings, in which:

FIG. 1 is a longitudinal cross section in schematic form, according to one implementation, of a guidance device in ring form for the mounting of a pin with friction and articulation capability; the ring is illustrated as before wear occurs, and the self-lubricating coating is symbolized by points.

FIG. 2 is a view in perspective of the ring, in accordance with the conditions in FIG. 1.

FIG. 3 is a longitudinal cross section of the ring after wearing of the coating over

a part of the bore, with the self-lubricating coating remaining in the cavities; the debris from the said coating of the worn area is mixing with the grease, and accumulates in order to lake part in lubrication.

FIG. 4 is a view in perspective of the ring, in accordance with the conditions in FIG. 3.

We have illustrated (FIG. 1) for example of implementation of a guidance device in the form of a cylindrical body (1) such as a ring, with a coaxial boring for the assembly and friction of a pin articulating and sliding in combination with the grease.

The grease is contained in the workings (1 a) in the bore of the ring. For example, the workings (1 a) can be composed of holes, cells, grooves, etc.

Moreover, the grooves can form a grid or chevrons. The cylindrical body (1) that constitutes the ring is implemented from any type of material with a high resistance to wear and/or seizure, and to corrosion under extreme operating conditions, notably in the presence of high pressure, corrosion and abrasion.

In a known manner, the cylindrical body (1)—notably its bore—can undergo any type of surface treatment.

You are reminded that, by guidance device, we mean any type of bearings, slides, rotary joints, etc.

According to a characteristic that is fundamental to the invention, a low-wettability, self-lubricating coating (3) is applied to all of the friction area of the bore of the ring (1), including in the workings (1 a) suitable to act as a grease reserve.

The result of these arrangements is that, after wearing of the self-lubricating coating layer (3) at the friction area of the bore—after a certain length of time of operation—the difference in wettability between the said friction area no longer having the coating and the workings suitable to act as a grease reserve but still having the coating naturally tends to draw the grease out of the said workings, so that it lubricates the said friction surface (FIGS. 3 and 4).

The low-wettability self-lubricating coating (3) can be based on PTFE, MoS2, Graphite, etc.

As explained above, after total consumption of the self-lubricating coating layer at its friction surface, the said coating is present only in the holes, cells or other means constituting the grease reserves.

The advantages come to the fore clearly in the description. We emphasize and remind you that it is consequently possible to use all the grease contained in the workings in the bore of the ring or other component at the friction surface, in order to lengthen the intervals of time at which lubrication can be carried out.

Note that the working suitable to act as a grease reserve can be positioned between grooves formed at each end of the ring's bore.

You are referred to the comparative tests below, between a ring in accordance with the state of the art—i.e. without self-lubricating coating—and a ring according to the invention, i.e. with a low-wettability coating applied at the friction surface and the workings suitable to act as a grease reserve.

Ring According to the State of the Art:

-   Type of pin: 16 NC 6 CT Ra: 0.4 -   Nature of the bearing: gridded ring -   Dimensions of bearing: Inside Ø: 30 mm, outside Ø: 36 mm, width of     the friction area: 20 mm -   Movement: alternating rotation over 100 degrees -   Pressure calculated at projected surface: 50 Mpa -   Sliding speed: 8 mm per sec -   Extreme pressure of grease: lithium soap, type SNR-LUB EP grade NLGI     2 -   Lubrication during assembly and then operation without additional     grease.

Result of Tests:

-   Number of oscillations before first increase in the friction factor:     160,000 cycles.

Ring According to the Invention:

-   Type of pin: 16 NC 6 CT Ra: 0.4. -   Nature of the bearing: gridded ring -   Dimensions of bearing: Inside Ø: 30 mm, outside Ø: 36 mm, width of     the friction area: 20 mm -   Movement: alternating rotation over 100 degrees -   Pressure calculated at projected surface: 50 Mpa -   Sliding speed: 8 mm per sec -   Extreme pressure of grease: lithium soap, type SNR-LUB EP grade NLGI     2 -   Lubrication during assembly and then operation without additional     grease.

Result of Tests:

-   Number of oscillations before fast increase in the friction     factor: >320,000 cycles (test stopped before its ending). 

1- Guidance device comprising a metal ring for assembly with friction and with capability for articulation and/or sliding of a pin, with a bore of the ring having workings suitable to act as a grease reserve at a friction area, wherein a low-wettability self-lubricating coating layer covers an entire surface of the bore, including in the workings suitable to act as a grease reserve, such that after wearing of the self-lubricating coating layer at the friction surface of the bore, a difference in wettability between the friction surface and the workings still having the coating layer draws out grease from the workings so as to lubricate the friction surface. 2- The guidance device according to claim 1, wherein the low-wettability self-lubricating coating layer is based on PTFE. 3- The guidance device according to claim 1, wherein the low-wettability self-lubricating coating layer is based on MoS2. 4- The guidance device according to claim 1, wherein the low-wettability self-lubricating coating layer is based on Graphite. 5- The guidance device according to claim 1, wherein the workings suitable to act as a grease reserves are composed of holes or cells. 6- The guidance device according to claim 1, wherein the workings suitable to act as a grease reserves are composed of grooves. 7- The guidance device according to claim 6, wherein the grooves form a grid. 8- The guidance device according to claim 6, wherein grooves form chevrons. 9- The guidance device of claim 1, wherein the workings suitable to act as grease reserves are positioned between grooves formed at each end of the bore. 